Operating instructions

4. How to Control the Frequency Converter

4.1. PPO Types

The PROFIBUS profile for frequency converters specifies a number of communication objects (Pa-

rameter Process data Objects, PPO), which are suitable for data exchange between a process

controller, such as a PLC, and frequency converters. All PPOs are defined for cyclic data transfer

(i.e. DP V0), so that process data (PCD) and parameters (PCA) can be transferred from the master

to the slave and vice versa. The figure below shows the PPO types available for the FC 100, 200

and 300.

PPO types 3, 4, 6, 7 and 8 are pure process data objects for applications requiring no cyclic pa-

rameter access. The PLC sends out process control data, and the frequency converter then

responds with a PPO of the same length, containing process status data. The first two bytes of

the process data area (PCD 1) comprise a fixed part present in all PPO types. The next two bytes

(PCD 2) are fixed for PCD write entries (par. 9-15 [1]), but configurable for PCD read entries (par.

9-16 [1]). In the remaining bytes, from PCD 3 and on, the process data can be parameterised

with process signals from the list on par. 9-23

Parameters for Signal

Select the signals for transmission from the master to the frequency converter in par. 9-15

PCD

Write configuration

(request from master to the frequency converter). Select the signals for trans-

mission from the frequency converter to the master in par. 9-16

PCD Read configuration

(re-

sponse: FC -> master).

PPO types 1, 2 and 5 consist of a parameter channel and process data. The parameter channel

can be used for reading and/or updating of parameters (successively). Alternatively, for better

utilisation of I/O and thus PLC capacity, parameters can be accessed via DP V1, in which case a

pure process data object should be chosen (PPO type 3, 4, 6, 7 or 8).

The choice of PPO type is made in the master configuration, and is then automatically recorded

in the frequency converter. No manual setting of PPO types in the frequency converter is required.

The current PPO type can be read in par. 9-22

Telegram selection

In addition, all PPO types can be set up as word consistent or module consistent. For FC 100, 200

and 300, the process data area can be word or module consistent, whereas the parameter channel

must always be module consistent. Module consistent data is transmitted as sets of interrelated

words transferred simultaneously between the PLC program and the frequency converter. Word

consistent data is transmitted as individual independent words between the PLC and the frequency

converter.

Selection [1]

Standard telegram 1

is equivalent to PPO type 3.

VLT

Profibus 4. How to Control the Frequency Converter

MG.33.C4.02 - VLT

is a registered Danfoss trademark